First, you need to backup your data , to boot windows you can use Super Grub2 Disk, witch allow you to boot a different OS , legacy or UEFI .
Because GRUB does not understand GPT partition tables, you need to create a
bios_grub partition then reinstalling Grub , also the
os-prober need to be installed to get the others OS detected.
Note: For GRUB to boot from a GPT-partitioned disk on a BIOS-based system, a BIOS boot partition is required. Please note that this partition is unrelated to the /boot mountpoint, and will be used by GRUB directly. Do not create a filesystem on it, and do not mount it.
What is the
The BIOS boot partition is a partition on a data storage device that GNU GRUB uses on legacy BIOS-based personal computers in order to boot an operating system, when the actual boot device contains a GUID Partition Table (GPT). Such a layout is sometimes referred to as BIOS/GPT boot.
A BIOS boot partition is needed because GPT uses the disk sectors immediately following the Master Boot Record (MBR) to hold the actual partition table, whereas the traditional MBR-based partitioning scheme does not designate them for any special purpose. As a result, there is not enough unused space available for storing second stages of boot loaders on GPT disks; boot loaders are usually implemented so their code stored within the MBR, which cannot hold more than 512 bytes, operates as a first stage that serves primarily to load a more sophisticated second stage, which is, for example, capable of reading and loading an operating system kernel from a file system.